Knob assembly for typewriter platen or the like



9 v D. HUMHREYs I I 3,461,997

KNOB ASSEMBLY FOR TYPEWRI TER PLATEN OR THE LIKE Filed Oct. 21, 1968 2 Sheets-Sheet 1 [nven for Don a ZzZIP. Humfih ra l s By his Attorney 7 Aug. 19, 1969 R. HUMPLHREYSI KNOB ASSEMBLY FOR TYPEWRITER PLATEN OR THE LIKE ,FiledOct. 21-, 1968 2 Sheets-Sheet United States Patent; O

3,461,997 KNOB ASSEMBLY FOR TYPEWRITER PLATEN OR THE LIKE Donald R. Humphreys, Topsfield, Mass., assignor to USM Company, Boston, Mass., a corporation of New Jersey Continuation-impart of application Ser. No. 662,700, Aug. 23, 1967. This application Oct. 21, 1968, Ser. No. 769,267

Int. Cl. B41j 19/96, 1 9/ 76; F16h 33/00 US. Cl. 197-121 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of application Ser. No. 662,700, filed Aug. 23, 1967, now abandoned.

BACKGROUND OF THE INVENTION The platen in typing machines or the like customarily has at one end a rotary knob and a pawl and ratchet mechanism for eifecting discrete line spacing, and release mechanism operable, for instance by means of an axial push button, for enabling the knob to turn the platen so that it may be freely adjusted about its axis without reference to the line spacing. While the known arrangements generally operate in satisfactory manner there are numerous occasions when it is desirable to be able more easily to select any desired angular position of the platen and with greater accuracy and rapidity. The present invention contemplates the combination with a rotary platen of coaxial, economical gearing for manually positioning the platen conveniently and precisely, the gearing comprising a harmonic drive actuator of the type generally disclosed for instance in United States Letters Patent No. 2,906,143, issued Sept. 29, 1959, in the name of C. Walton Musser.

SUMMARY OF THE INVENTION A primary object of this invention is to provide an improved knob assembly whereby an operators finger movements may optionally angularly adjust a platen in coarse steps, or, with similar operating movement applied to a difierent portion of the assembly, angularly adjust in refined increments. To the end stated, afeature of the invention resides in the combination with a carriage having a rotatable platen and detent means for controlling rotation of the platen about its axis, of knob means coaxially mounted on an axial extension of the platen for optionally rotating the platen with coarse or fine adjustment, said knob means comprising a coarse adjusting member rotatable on the extension and having a sprocket cooperative with the detent means and circular spline teeth axially spaced from said sprocket, a flexible spline secured to the extension outboard of said member and having internal spline teeth meshing at circumferentially spaced localities with the circular spline 3,461,997 Patented Aug. 19, 1969 teeth and greater in number than the circular spline teeth, and a fine adjusting knob having an internal wave generator portion axially extending into the member for circumferentially progressing the localities of spline tooth engagement and hence rotation of the flexible spline relative to the member.

In the arrangement just indicated the fine adjusting knob is outboard of the coarse adjusting knob and its associated sprocket, but in accordance with a further feature of the invention the coarse adjusting knob may, in an alternate arrangement, be outboard of the line adjusting knob. Unlike the arrangement first indicated wherein the flexspline acts as the output member during fine adjustment, in the alternate arrangement the flexspline is stationary and the circular spline functions as the output member.

BRIEF DESCRIPTION OF THE DRAWING The foregoing and other features of the invention will now be described with more particularity in connection with two illustrative embodiments and with reference to the accompanying drawing, in which:

FIG. 1 is a view in side elevation of a left-hand portion of a typewriter platen with its control knob assembly, a portion of the latter being broken away and in section to reveal internal construction;

FIG. 2 is a section taken on the line IIII of FIG. 1;

FIG. 3 is a view similar to FIG. 1 but showing a modified arrangement of the parts permitting finger tip fine adjusting; and

FIG. 4 is a section taken on line IV-IV of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, a roller or platen '10 is mounted for rotation about its axis in a typewriter carriage comprising a pair of axially spaced brackets 12 only one of which is shown in FIG. 1. The platen 10 has an axial extension 14 journaled in the bracket 12 for coaxial-1y supporting a knob assembly, later to be described, by means of which angular adjustment of the platen 10 may be manually controlled.

The coarse or main adjusting knob 16 is axially bored to receive the extension 14 which is relatively rotatable therein. A right-hand portion of the coarse knob 16, as seen in FIG. 1, has a sprocket 20 for cooperating in conventional manner with line spacing mechanism (not shown) and a detent roll 22, the latter normally seating between successive or selected teeth of the sprocket 20 to index it. A cover 24, only partly shown in FIG. 1, may be provided to exclude dust. For refined platen adjusting purposes to be explained, the knob 16 has a circular set of axial spline teeth 26 externally disposed on an internal hub 28.

A hollow flexspline 30 is mounted and keyed as at 29 (FIG. 2) on the extension 14 and serves as an output member for finely adjusting rotation of the platen 10 as will be described. For this purpose an extension flat 18 abuts a corresponding flat 31 internally formed in the flexspline 30. A radially deflected circumference of the flexspline 30 is internally formed with circularly arranged spline teeth 32 greater in number than the teeth 26 in accordance with harmonic drive actuator design principles as disclosed, for instance in the abovementioned Musser patent. A cup-shaped fine adjusting knob 34 outboard of the flexspline 30 and the coarse adjusting knob 16 has its perimeter axially extending into a recess 36 of the knob 16. This enables an internal wave generator surface 38 formed on the knob 34 to engage the flexspline 30 radially opposite to its localities of spline engagement with the circular spline teeth 26. For purposes of illustration the surface 38 is shown as elliptoidal and thus dimensioned to deflect the fiexspline teeth 32 radially inward at diametrically opposite localities of meshing. It will be understood that in accordance with known harmonic drive construction, the surface 38 may alternatively be trilobar for effecting three meshing localities, or otherwise multilobar, providing a suitable difference in the number of teeth 36 and 32 is maintained.

Since it is contemplated that for economy in design the parts may be molded of suitable plastic, lobar configuration of the wave generator surface 38 is preferably stiffened and retained by use of a resilient circular wire or band insert 40 extending about 350 and nested in confronting grooves 42, 44 (FIG. 2) in the knobs 34 and 16, the insert 40 further serving to hold the two knobs 34, 16 against axial separation.

In operation a typist will rotate the knob 16 correspondingly to adjust the platen about its axis, the detent roll 22 or other click means holding the platen in selected discrete position determined by the sprocket teeth of sprocket 20. The platen 10 rotates in 1:1 ratio with the knob 16 because the teeth 32 of the fiexspline 30 mesh with the teeth 26 on the hub 28 of the knob 16 and are driven by the latter. Harmonic drive is not then occurring. If refined positioning of the platen 10 is desired the typist merely rotates the knob 34. The knob 16 now is relatively stationary, the detent roll 22 serving as a reaction member as the wave shape of the surface 38 is rotated circumferentially to progress the localities of engagement of the fiexspline teeth 32 with the nonrotating teeth 26. By reason of the tooth differential the fiexspline 30 is itself rotated to drive the extension 14 at a much reduced ratio, commonly about 50:1, for instance, in the case of an elliptoidal surface 38. Thus with very little finger effort, and with finger movements essentially like the adjusting motion which may first have been applied to the main knob 16, the platen 10 is rotated with infinitely fine adjustment to the desired position.

FIGS. 3 and 4 show an alternate arrangement wherein a coarse adjusting knob 50 is secured on a fiat 53 on the outboard end of an axial extension 52 aflixed to a rotatable platen 54. In this case the typewriter carriage comprises spaced roll supporting brackets 56 (one only shown in FIG. 3) and a cover 58 through which the knob 50 and the extension 52 project. A sprocket 60 freely rotatable on the extension 52, a detent roll 62 and other portions of this knob assembly are within the cover 58 except for an upper peripheral portion 64 of a fine adjusting knob 66 which extends through a slot 67 (FIG. 3) in the cover 58. The knob 66 rotatably mounted on an axial hub 68 of the sprocket 60 is formed with an internal wave generator surface 70 which may be elliptoidal as indicated in FIG. 4 or otherwise lobar as above indicated. In this case the wave generator surface 70 radially deflects internal spline teeth 71 of a cup-shaped fiexspline 72 secured to the sprocket hub '68 into meshing engagement diametrically opposite localities with external circular spline teeth 74 formed on the coarse adjusting knob 50. A larger number of fiexspline teeth than circular spline teeth 74 is provided, the difference being two or a multiple thereof, unless a different wave generator shape is employed.

In using the arrangement shown in FIG. 3, the knob 50 will normally first be used for coarse adjusting of the platen 54. Much finer adjusting is attained by turning the knob 66 by engaging its exposed portion 64. This rotates the wave generator 70 relative to the fiexspline 72 which is now relatively stationary. Accordingly the localities of spline engagement are circumferentially progressed with reduced output in the knob 59 which accordingly transmits the slower refined rotation through the extension 52 to the platen 54.

Either of the foregoing illustrative arrangements may be inexpensively mounted on standard business machines having rollers to be angularly adjusted. Advantageously the parts are inexpensively manufactured, easily assembled, and provide no problems in maintenance.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a typewriter or the like having a rotatable platen and detent means for controlling rotation of the platen about its axis, an axial extension of the platen, and coaxial knob means mounted on the extension for optionally rotating the platen with coarse or infinitely fine increments, said knob means comprising acoarse adjusting member rotatable on the extension and integrally having a sprocket cooperative with the detent means and circular spline teeth axially spaced from the sprocket, a fiexspline secured to the extension outboard of the adjusting member and having internal spline teeth meshing at circumferentially spaced localities with the circular spline teeth and greater in number than the circular spline teeth, and a fine adjusting knob having an internal wave generator surface axially extending in the coarse adjusting member for circumferentially progressing the localities of spline tooth engagement and hence rotation of the fiexspline and the platen relative to the coarse adjusting member.

2. A typewritter or the like as set forth in claim 1 wherein a resilient circular insert is arranged between the coarse adjusting member and an exterior portion of the fine adjusting knob for aiding in retention of the wave generator surface shape in the latter.

3. In a typewriter or the like having a rotatable platen and detent means for controlling rotation of the platen about its axis, an axial extension of the platen, a coarse adjusting knob secured outboard of the extension and having circular spline teeth formed thereon, a sprocket rotatable inboard on the extension and cooperatively engageable with the detent means, said sprocket having an axial collar, a fine adjusting knob journaled on said collar and having an internal wave generator surface, and a fiexspline coaxially mounted on the sprocket for rotation therewith, the arrangement being such that axial spline teeth of the fiexspline are greater in number than the spline teeth of the coarse adjusting knob and are in mesh therewith at circumferentially spaced localities as determined by said wave generator surface, whereby rotation of the fine adjusting knob acts with reduced ratio through the coarse adjusting knob to angularly move the platen.

References Cited UNITED STATES PATENTS 1,056.703 3/1913 Lux. 1,136,223 4/1915 Fraaz. 1,189,743 7/ 1916 Schwartz. 1,381,143 6/1921 Tingley. 2,93 0,254 3/1960 Musser et al. 2,932,986 4/ 1960 Musser. 2,943,513 7/ 1960 Musser. 3,187,862 6/ 1965 Musser.

ERNEST T. WRIGHT, JR., Primary Examiner US. Cl. X.R. 

